1. Field of the Invention
The present invention relates to a semiconductor device including a plurality of input buffers to which internally-generated reference voltages are applied.
2. Description of the Related Art
Generally, in a semiconductor device, a plurality of input buffers are constructed by differential amplifiers for amplifying the difference between input voltages and respective reference voltages. Also, in order to decrease the number of external pads, the reference voltages are generated within the semiconductor device. In this case, the reference voltages are important parameters for determining whether the operation of the input buffers is normal or abnormal, i.e., whether the semiconductor device is normal or abnormal. Therefore, each of the input buffers monitors its reference voltage which is transmitted to an external pad in a test mode. This will be explained later in detail.
In the above-described prior art semiconductor device, however, the larger the number of input buffers, the larger the number of external pads for monitored reference voltages. For example, if the semiconductor device constitutes a processor, the number of input buffers is several hundreds. As a result, the semiconductor device including such input buffers would be increased in size.
It is an object of the present invention to provide a semiconductor device having a plurality of input buffers with a reduced number of external pads.
According to the present invention, a semiconductor device is constructed by at least one reference voltage generating circuit for generating a reference voltage, a plurality of input voltage pads for receiving input voltages, a control signal pad for receiving a control signal, and a plurality of input buffers. Each of the input buffers amplifies a difference between one of the input voltages and the reference voltage to generate an output voltage, and includes a switch connected between the reference voltage generating circuit and one of the input voltage pads and controlled by the control signal.
Thus, the reference voltage is transmitted by the control signal from the reference voltage generating circuit to the input voltage pads.